I have two levels of backup mail servers. The first run by a friend of mine, the second run by my ISP. My MX records are set up as follows:
domain.org. MX 5 mail.domain.org. domain.org. MX 10 mail.friend.org. domain.org. MX 20 mail.isp.net. I have access to the mail configurations on the primary and (by proxy) the secondary server, both of these running Exim 4. I have no control over the tertiary server at the ISP, though I have confirmed that it does forward mail to me as expected. The problem occurs when my primary server goes out, leaving the other two alive. At that point, the secondary server (mail.friend.org) gets my mail and looks up the available MXes. Since mail.domain.org is not available, but mail.isp.net is, mail.friend.org immediately forwards it on to the tertiary server (mail.isp.net). This server then sees that mail.domain.org is not available, but mail.friend.org is, and as such forwards the mail there. At this point the cycle repeats, causing a mail loop and, eventually, bounced mail messages. My question, then, is this: How do I configure mail.friend.org to only forward to mail.domain.org and never to mail.isp.net? Or, more generally, how do I configure the server to send to MX servers *only* of higher priority than itself? I tried setting "hosts_treat_as_local" to include the domain name and then the IP addresses of the tertiary server, but then the secondary server just bounced mail back immediately instead of queueing it for later delivery. I'm guessing that's since it saw no other available servers to send to? Thank you, - Justin Richer -- ## List details at http://www.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://www.exim.org/eximwiki/
